There is an increasing interest to investigating single cells, especially over substantial time periods (e.g., days). Microfluidics allows for numerous and creative solutions. In some embodiments, small populations or even single cells are organized into grids, or other organized geometries, where time lapse microscopy and other analyses may be used to monitor and analyze these cells (e.g. monitor their number, morphology or fluorescence variation over time.) In some microfluidic experiments, cells are separated physically or chemically.
Microfluidic devices separate and or interact with cells, other biomolecules, samples, or reagents both spatially and via chemical reactions. Microfluidic devices may offer further insights into the cellular machinery, without the limitation of biochemical cross-talking.
Microfluidic devices are designed to precisely control and manipulate fluids in a geometrically constrained platform. Channels in some devices are microns wide or narrower. Liquids in these channels may be measured in nanoliters or picoliters, i.e., the scale of some typical laboratory science experiments or in inkjet printers.
In some known microfluidic devices the geometric constraints promote environments distinct from those in non-microfluidic devices. The microfluidic environment may differ from the non-microfluidic environment in such ways as laminar flow, surface tension, energy dissipation, diffusion, and fluidic resistance. In a microfluidic environment the flow rate of fluids may be inversely proportional to the square of the area of the channel cross section. In a microfluidic environment fluids may not mix, even when situated side-by-side to one another.
Some known microfluidic devices use capillary action to control or manipulate fluids. Other devices use micropumps or microvalves. Microfluidic devices provide for numerous applications, including for use in biological reactions and the analysis of biomaterials.
Microfluidic devices may be constructed using a variety of manufacturing methods, one such method being, for example, soft lithography. A soft lithography process generally refers to the construction of devices, wherein the construction may employ some techniques similar to standard lithography, i.e., the use of light to transfer structure detailed in a mask onto a silicon wafer. Soft lithography typically employs an elastomer, e.g., a polymer with visco-elasticity, most notably polydimethylsiloxane (PDMS). Soft lithography is generally used to construct features from a wafer die containing a desired pattern, e.g., a pattern that may be appropriate in a microfluidic device, or a stamp for creating such a pattern.
Microfluidics may enable portable analysis devices with short sample-processing times. Microfluidics may provide lab-on-a-chip point-of-care functionality. For example, medical analyses may be able to be conducted at or near the site of the patient care. Other functionality may include immuno-assays, nucleic acid based molecular diagnostics, including application of reverse transcription polymerase chain reaction (RT-PCR) or florescence in-situ hybridization (FISH).